--- a/js/src/asmjs/WasmBinaryToAST.cpp
+++ b/js/src/asmjs/WasmBinaryToAST.cpp
@@ -89,17 +89,18 @@ class AstDecodeContext
        generateNames(generateNames),
        numTableElems(0),
        initialSizePages(),
        maxSizePages(),
        module_(module),
        funcSigs_(lifo),
        iter_(nullptr),
        locals_(nullptr),
-       blockLabels_(lifo)
+       blockLabels_(lifo),
+       currentLabelIndex_(0)
     {}
 
     AstModule& module() { return module_; }
     AstIndexVector& funcSigs() { return funcSigs_; }
     AstDecodeExprIter& iter() { return *iter_; }
     const ValTypeVector& locals() { return *locals_; }
     AstNameVector& blockLabels() { return blockLabels_; }